Transcoding bug with PWA

[rhaker]

One of my users can't transfer calls, when they do this error is displayed:

Failed to execute 'setRemoteDescription' on 'RTCPeerConnection': Failed to parse SessionDescription, a=rtpmap: 2 G726-32/8000 Duplicate statistically assigned payload type with contradicting codec name or clock rate.

The trunk is set to G711A only as specified by the trunk provider, adding G726 does not fix the issues (G726 is rejected).

On a fixed phone I can remove G726 from the supported codecs list which would fix the issue, but the user only has the PWA app for which you cannot specify supported codecs.

 

[JohnS_3CX]

Hi,

You are involving a 3rd party that uses an unsupported codec - this should be removed from your end. Are you using a Grandstream phone or FXS?

Please explain in detail the exact call flow, what devices are involved, models, and exact firmware versions, and whether you use custom templates.

 

[rhaker]

No physical phones are involved, only PWA and a SIP trunk.

 

[JohnS_3CX]

When you transfer a call however is it trunk, to PWA, to trunk again?

What does the 3rd party in the transfer use?

 

[rhaker]

The traffic flows as follows:

external caller -> SIP Trunk -> PWA -> transfer -> PWA

 

[JohnS_3CX]

Ok then this means it must be coming from the provider side (even if you selected only G.711).

The provider should not really be sending that payload type as it is considered reserved.

1. What provider is it, unsupported?
2. Was the template modified (if supported provider)?
3. Does the trunk have PBX delivers audio?

Whichever the case, if you enable PBX delivers audio on the trunk (like all supported providers have) you should stop seeing this.